DISEASES OF THE HOUSE. l75 



will grow out in a newt when the former has been cut off. In the 

 early embryo, with its g-ieat powers of development, this factor can 

 operate to far greater purpose than in the adult animal. Its iniluence 

 is seen in the fact pointed out by St. Ililaire that such redundant parts 

 are nearly alwa3^s connnected w^ith the corresponding portions in the 

 normal fetus. Thus superfluous legs or digits are attached to the 

 normal ones, double heads or tails are connected to a common neck or 

 rump, and double bodies are attached to each other b}^ corresponding 

 points, navel to navel, breast to breast, back to back. All this sug- 

 gests the development of extra parts from the same primary layer of 

 the impregnated and developing ovum. The effect of disturbing con- 

 ditions in giving such wrong directions to the developmental forces is 

 w^ell shown in the experiments of St. Hilaire and Valentine in varnish- 

 ing, shaking, and otherwise breaking up the natural connections in 

 eggs, and thereby determining the formation of monstrosities at will. 

 So, in the mammal, blows and other injuries that detach the fetal 

 membranes from the walls of the womb or that modify their circula- 

 tion by inducing inflammation are at times followed by the develop- 

 ment of a monster. The excitement, mental and ph3'sical, attendant 

 on fright occasionally acts in a similar wa}^, acting probably through 

 the same channels. 



The monstrous forms likely to interfere with parturition are such 

 as, from contracted or twisted limbs or spine, must be i^resented double; 

 where supernumerary limbs, head, or body must approach the pass- 

 ages with tlic natural ones; where a head or other member has attained 

 to an unnatural size; where the body of one fetus has become inclosed 

 in or attached to another, etc. 



Extraction is sometimes possible by straightening the members and 

 securing such a presentation as will reduce the presenting mass to its 

 smallest and most wedge-like dimensions. To effect this it may be 

 needful to cut the flexor tendons of bent limbs or the muscles on the 

 side of a twisted neck or body; and one or more of the manipulations 

 necessary to secure and bring up a missing member may be required. 

 In most cases of monstrosity by excess, however, it is needful to 

 remove the superflous parts, in which case the general principles 

 employed for embryotomy must be followed. The Co?sarean section, 

 by which the fetus is extracted through an incision in the walls of the 

 abdomen and womb, is inadmissible, as it practically entails the sacri- 

 fice of the mare, Avhich should never be done for the sake of a monster. 

 (See "Embrj'otomy," p. 181.) 



ENTRANCE OF TV.INS INTO THE PASSAGE AT ONCE. 



Twins are rare in the mare, and still more rare is the impaction of 

 both at once into the pelvis. The condition would be easil}- recognized 

 bj^ the fact that two fore limbs and two hind would occupy the passage 



